BooleanPolynomial.variables() consider "1" as a variable

[sagetrac-Bouillaguet]

This is in contradiction with other functions (BooleanPolynomial.nvariables), and with the behavior of the "normal" class MPolynomial.

Example:

sage: R.<x,y,z> = BooleanPolynomialRing()
sage: p = R(1)
sage: p.variables()
(1,)
sage: p.nvariables()
0

Which differs from:

sage: R.<x,y,z> = GF(2)[]
sage: p = R(1)
sage: p.variables()
()
sage: p.nvariables()
0

CC: @malb @alexanderdreyer @sagetrac-PolyBoRi

Component: commutative algebra

Keywords: BooleanPolynomial

Author: Charles Bouillaguet

Reviewer: Alexander Dreyer, Martin Albrecht

Merged: sage-5.1.beta6

Issue created by migration from https://trac.sagemath.org/ticket/13104

[sagetrac-Bouillaguet]

Attachment: pbori_variables.patch.gz

patch that fixes the problem

[malb]

comment:2

Hi, can you add a doctest that shows that the issue is resolved? I also CCed the PolyBoRi developers to make sure there isn't some obscure reason for this behaviour.

[sagetrac-Bouillaguet]

comment:3

Hi,

I actually did, in fact. I modified the existing docstring to verify that:

sage: P.one_element().variables()  
()

Should I add anything else?

[malb]

comment:4

Sorry, my bad!

[alexanderdreyer]

comment:5

p.variables() is a Sage extension (see #1715), the corresponding p.vars_as_monomial() () already behaves like this. (I think in early versions of PolyBoRi p.vars_as_monomial() could become 0, but this was a design error.) So I can clearly give a positive review.

[malb]

Author: Charles Bouillaguet

[malb]

Reviewer: Alexander Dreyer, Martin Albrecht

[jdemeyer]

Merged: sage-5.1.beta6